For high quality, high density color displays, colors are generally stored as 24 bit values, with red, green and blue separations. Each separation N.sub.x is typically an 8 bit value, so that the color of each pixel is identified as a value in the range of 0-255 for each separation that forms the image. For example, a value of 0 for the red separation means that there is no red in the pixel, while a value of 255 means that the pixel has fullest amount of red it may have. In a 24 bit/pixel color system there are (256).sup.3 or approximately 16 million possibilities of color for each pixel in a color image.
It is often desirable to alter or vary color in luminance/chrominance space. However, with 16 million possibilites of color in RGB space for each pixel, where each pixel in the image would require conversion to a luminance/chrominance value, real time editing of the image on a display presents significant difficulties. Another approach would be to a very high speed computer, but this approach is not economically desirable. Additionally, while the image is usually displayed in RGB color space, modification of RGB images with direct control of each separation is not intuitive to the casual user of such a system.
U.S. patent application Ser. No. 07/404,395 by Venable et al., entitled "Color Set Selection and Color Imaging", teaches a method of selecting an optimum color set for such color imaging system, while maintaining the impression of full color.
U.S. Pat. No. 4,725,828 to Cowlinshaw shows a method of displaying and coding a color image wherein a number of levels are provided to encode the image using error diffusion. The proportions of red, green and blue in each pixel are varied by bit boundaries dependent on eye sensitivity. U.S. Pat. No. 4,564,915 to Evans et al. discloses a chrominance/luminance computer color graphics system, wherein a frame buffer is used to store color images, and a conversion matrix is provided to convert between RGB and chrominance/luminance color space. U.S. Pat. No. 4,739,313 to Oudshoorn et al. discloses a multilevel grey scale or composite video to RGBI decoder wherein 6 levels are used to define a gray scale as well as a RGBI space. U.S. Pat. No. 4,727,425 to Mayne et al. discloses a color modification table for use in image reproduction systems, where tables are provided for four color components. U.S. Pat. No. 4,694,286 to Bergstedt shows an on-screen user interface for altering hue, lightness, and saturation values for any pixel.
All the references cited hereinabove are specifically incorporated by reference.